An OED is a device including at least one organic material layer enabling current conduction. Types of the OED include an organic light emitting device (OLED), an organic photovoltaic cell, an organic photo conductor (OPC), or an organic transistor.
Conventionally, a representative OED such as an OLED, sequentially includes a substrate, a transparent electrode layer, an organic layer and a reflective electrode layer. In a structure called as a bottom emitting device, the transparent electrode layer may be formed as a transparent electrode layer, and the reflective electrode layer may be formed as a reflective electrode layer. In addition, in a structure called as a top emitting device, the transparent electrode layer may be formed as a reflective electrode layer, and the reflective electrode layer may be formed as a transparent electrode layer. Electrons and holes are injected by the electrode layer, and recombined in an emitting unit present in an organic layer, thereby generating light. The light may be emitted to the substrate or the reflective electrode layer. In the structure of the OLED, light generated from the emitting unit due to the difference in refractive index between indium tin oxide (ITO) generally used as a transparent electrode layer, the organic layer and the substrate is trapped at an interface between the organic layer and the transparent electrode layer or in the substrate due to total internal reflection, and only a very small amount of light is emitted. Accordingly, while several methods are proposed to solve this problem, the methods that have been proposed so far are applied to structures using a rigid substrate such as a glass substrate, and a variety of research on a structure for a flexible device is progressing.
An important issue to consider for the OED is durability. Since the organic layer or an electrode may be very easily oxidized by an external material such as water or oxygen, it is important to ensure durability with respect to an environmental factor. To this end, for example, structures for preventing permeation of external materials are proposed in the patent documents 1 to 4. Problems relating to the durability can also be more seriously shown in a flexible structure using a base conventionally having a lower barrier property than glass.